1. Technical Field
The present invention relates to automatic transmissions.
2. Background Art
An automatic transmission in an automotive vehicle power-train adjusts a gear ratio between a torque source and a driveshaft to meet drive-ability requirements under dynamically-changing driving conditions. The shifting of the transmission is accompanied by applying and/or releasing transmission friction elements (such as clutches, band-brakes, etc.) which change speed and torque relationships by altering planetary gear configurations. As a result, power flow paths are established and disestablished from an internal combustion engine to vehicle traction wheels.
The actuation of the friction elements has to be properly controlled in order to carry out the shifting of the transmission. For instance, during an up-shift event in a synchronous automatic transmission, the on-coming clutch (“OCC”) engages as the off-going clutch (“OGC”) releases. That is, as the torque transmitted through the OCC torque increases, the load exerted onto the OGC torque decreases due to a kinematic arrangement of gear sets. The release timing of the OGC has to be synchronized with a certain OCC torque level or else the shift quality may be inconsistent. Information regarding the operation of the transmission may be monitored and used to control the OCC and the OGC in order to carry out the shift event.
In general, monitored information regarding the operation of an automatic transmission may be used for the control of the power-train and the drive-train with the intent to, among other factors, improve drive-ability, shift quality, and fuel economy. Thus, it is desired that only the monitored information which is accurate is used for control operations.